Apron for a piston machine



FIG. 1 is a perspective view of the apron for a piston machine;

FIG. 2 is a top plan view;

FIG. 3 is a side elevational view thereof;

FIG. 4 is a bottom plan view thereof; and,

FIG. 5 is an end elevation view. 

The ornamental design for a apron for a piston machine, as shown and described. 